CAEBONIFEROUS UNDIVIDED. 373 



following forms have been reported: Fenestella, Orthothetes [Schuchertella], Leptsena, Spirifer, 

 Chonetes logani, Reticularia peculiaris, Syringothyris carteri, and crinoids. It is correlated with 

 the Chouteau or Kinderhook of the Mississippi Valley. 



The Pahasapa limestone (Mississippian), directly overlies the Englewood lime- 

 stone (also Mississippian), into which it merges. It is a massive gray limestone 

 without noteworthy subdivisions, varies in thickness from 225 to 500 feet, and 

 according to Darton contains Spirifer rockymontanus, Seminula dawsoni {Athyris 

 suUilita), Productus and Zaphrentis. 



Darton ^'^ describes the Minnelusa sandstone as follows: 



The Minnelusa formation consists mainly of thick beds of gray, buff, and reddish sand- 

 stones, usually fine grained, most of which, in their unweathered condition, contain a consid- 

 erable proportion of carbonate of lime. Thin sheets of limestone occur in some districts and, 

 less frequently, sandy shales of red or gray color. Some layers are cherty. * * * [The 

 formation] is thickest on the western side [of the Black Hills], where it is fuUy 750 feet, and it 

 thins gradually to the south and east, being about 400 feet thick in the southeastern portion of 

 the uplift. 



On the evidence of "indistinct casts" of Productus semireticulatus and SeminuM 

 dawsonii (Athyris subtilita), ''recognized with a fair degree of certainty," the upper 

 part of the IVIinnelusa sandstone is assigned to the Pennsylvanian. The lower 

 part, if correctly correlated with the lower part of the Hartville formation,^''' is 

 ]yiississippian. 



The IVTinnelusa sandstone is succeeded by the Opeche formation (Permian) . (See 

 pp. 495-496.) 



The relations of the Carboniferous of the Black Hills to that of the Laramie and 

 Hartville ranges of Wyoming are thus discussed by Darton :^'^ 



Along the Laramie Range the apparent absence of Lower Carboniferous is an intei-esting 

 feature, indicating either nondeposition or removal by the very profound later [middle] Car- 

 boniferous erosion. A short distance eastward, in the Hartville uplift, there are comprised 

 in the Mississippian the Guernsey formation, 150 feet or more in thickness, and the lower mem- 

 bers of the Hartville formation, the two formations being separated by strongly marked ero- 

 sional unconformity. The basal sediments of the Hartville formation are red sands, and there 

 is strong suggestion that these are of the same age as the red shale at the base of the Minnelusa 

 formation of the Black Hills and base of the Amsden formation in the Bighorns. The represen- 

 tative of the Lower Carboniferous in Colorado appears in the small areas at Perry Park, about 

 Manitou, about Canyon City, and southwest of Pueblo, and is known as the Millsap limestone. 

 This limestone lies unconformably on the Cambrian, Ordovician, and pre-Cambrian and is 

 unconformably overlain by the Fountain [PottsviUe age] or lower Wyoming formation, which 

 overlaps directly on the granites in most portions of the area. Its fauna is regarded as 

 moderately early Mississippian. 



K 10. KLAMATH MOUNTAINS, CALIFORNIA. 



The Klamath Mountain section includes, according to Diller,^^^'^'^ several 

 Carboniferous terranes — Bragdon formation, basal Mississippian of the region- 

 Baird formation (Mississippian) ; McCloud limestone and Nosoni formation (includes 

 the "McCloud shales"), Pennsylvanian; and limestones of the Hall City locahty 

 which are Permian. 



